The present invention relates to a sheet cutting device that cut several sheets of paper, to a sheet finishing apparatus equipped with the sheet cutting device, and to an image forming systems provided with the sheet finishing apparatus.
A Sheet finisher carrying out various types of finishing is connected to a high speed image forming apparatus such as an image forming apparatus employing the electro-photography method, and multiple-functional image forming systems have come into wide use that make it possible to carry out within a single apparatus various types of finishing operations such as stapling and folding of paper sheets on which images have been formed.
Among the different types of finishers there is the sheet cutting apparatus that aligns the edges of a bundle of a plurality of sheets, and an image forming system having a sheet cutting apparatus that cuts the edges of sheets that have been subjected to center-folding and center-stapling has been disclosed, for example, in Japanese Unexamined Patent Application Laid-Open No. 2003-228205. The sheet cutting apparatus disclosed in the Japanese Unexamined Patent Application Laid-Open No. 2003-228205 is of the type commonly referred to as the guillotine type and is one in which the cutting done by pressing the cutting blade from a direction perpendicular to the sheet surface.
In the sheet cutting apparatus disclosed in Japanese Unexamined Patent Application Laid-Open No. 2003-136471, there is a sheet pressing member that presses the bundle of sheets including a plurality of sheets placed one upon the other so that the position of the bundle of sheets does not get shifted, the cutting blade (cutter) is placed below the sheet pressing member and can move in a diagonally upward direction. A link is attached to the sheet pressing member so that it can be raised or lowered using a drive section. In this sheet cutting apparatus, the positioning of parts is made so that the central position of the load application action of the sheet pressing member capable of being raised and lowered is almost directly above the cutting edge of the cutter.
Since the guillotine type of sheet cutting apparatus described in the Japanese Unexamined Patent Application Laid-Open No. 2003-228205 cuts the bundle of sheets by moving the cutting blade in a direction perpendicular to the sheet surface, a large force is required for driving it. And also, since it is necessary to set the power of the driving section at the maximum value in the usable range, there is the requirement for a large power and large sized motor and a power supply with a large power capacity resulting in the problems that not only the apparatus becomes large but also the power consumption becomes large. In particular, it becomes difficult to incorporate a sheet cutting apparatus in a sheet finishing apparatus that is a part constituting an image forming system.
In the sheet cutting apparatus disclosed in the Japanese Unexamined Patent Application Laid-Open No. 2003-136471, since the central point of the lower surface of the sheet pressing member is in a state in which it has projected beyond the edge surface of the table supporting the bundle of sheets, at the time of cutting the edge of the bundle of sheets by raising the cutting blade in a diagonally upward direction while pressing the sheets placed on the table using a sheet pressing member, it is likely that the sheet pressing member becomes inclined thereby applying a load on the cutter. In particular, at the time of cutting a number of sheets of paper such as when cutting 50 to 100 sheets, an abnormally high load may be applied on the cutting blade. Because of this, the driving load of the cutting blade moving section becomes large. In addition, the cut edge surface of the bundle of sheets does not become perpendicular to the sheet surface and the sheets do not become aligned, thereby lowering the quality of the finished booklets.